Drivers of vehicles are often unaware of approaching emergencies, such as an emergency vehicle. As they drive, drivers may be listening to loud music, talking on a phone or to a passenger, focused on the road ahead, etc. Also, modern vehicles are insulated against outside noise, and in the future, vehicles will likely be better insulated against outside noise. A driver is often unaware of an approaching emergency vehicle until the vehicle is very close or is actually trying to pass the driver's vehicle. The driver's delay in acting to move over to allow the emergency vehicle to pass or a startled reaction of the driver in noticing the emergency vehicle may result in an accident.
In busy noisy cities, in particular, drivers may be unaware of approaching emergency vehicles due to the additional concentration required for driving. In these areas, drivers often unintentionally block emergency vehicles, leading to delays in the response time of the emergency vehicles.